The Clock - Season 3 (1950)

A taut drama of a man's race against time to avert the tragic death of a young girl. Leslie Nielsen stars as David Kyle, a clerk on the night shift in a Grand Central Terminal drug store. He prescribes a car sickness cure for a pretty young bride-to-be, stopping overnight in New York between trains. Another customer orders mercuric nitrate for a skin ailment, then takes the girl's medicine by mistake. The girl leaves with the mercuric nitrate, which is poison if taken internally. When Kyle discovers the error, he enlists the aid of the police and the stationmaster in trying to find the girl, whose name he doesn't even know, before she takes the deadly potion.